Mastering the Sentence Correction portion of the Verbal section involves learning about thirty rules of grammar, and then recognizing when these rules are incorrectly followed in long sentences. Often, these broken rules are easily identified by common patterns among GMAT questions. Learning to spot these error indicators not only results in earning more points, but also increases your speed and efficiency during the test, leaving more time for other questions.

The following article explains three common error indicators on the GMAT. These errors have appeared many times on the GMAT, and are likely to appear often on future exams. Recognizing these errors and understanding how to correct them can increase your verbal score.

The word number is singular. However, the object of the preposition of will often be plural, as in:

The number of houses
The number of students
The number of cases

The use of a plural object (houses, students, cases) often leads students to choose a plural verb:

The number of housesare increasing. (Incorrect)
The number of studentsare twice that as last year. (Incorrect)
The number of caseswere a direct reflection of the crime rate. (Incorrect)

However, all three of these sentences are grammatically incorrect. The object of the preposition is not the subject of the sentence. The subject is the singular number. Therefore, all three verbs should be singular:

The number of houses is increasing. (Correct)
The number of students is twice that of last year. (Correct)
The number of cases was a direct reflection of the crime rate. (Correct)

To make the sentences even more difficult, the makers of the GMAT will usually try to separate the subject (number) from the verb by using long phrases, many of which will contain more plural nouns:

The number of houses on the three blocks is increasing. (Correct)
The number of students attending the school dances is twice that of last year. (Correct)
The number of cases that were brought in front of judges was a direct reflection of the crime rate. (Correct)

In the first sentence, the use of the noun blocks causes the verb is to sound awkward. The same is true for the second sentence due to the word dances. However, since the subject is number, the verb is singular. You would be wise to immediately check subject verb agreement if you see the phrase “the number of….”

An introductory adjective clause is a phrase placed at the beginning of a sentence that modifies a noun. Consider an example:

First released in 1913, the buffalo nickel was minted for twenty-five years. (Correct)

In this sentence, first released in 1913 is an introductory adjective clause that modifies buffalo nickel. What was first released in 1913? The buffalo nickel.

Let’s look at another:

Using the Fujita Scale, scientists rate a tornado’s intensity. (Correct)

In this sentence, using the Fujita Scale modifies scientists. Who uses the Fujita Scale? Scientists.

When an introductory adjective clause is present, the noun being modified must be located right after the adjective clause. Problems arise when the noun is placed elsewhere in the sentence:

First released in 1913, the United States Mint produced the buffalo nickel for twenty-five years. (Incorrect)

According to this sentence, what was first released in 1913? The US Mint. This is incorrect. The buffalo nickel was first released in 1913, and thus nickel should be the first noun to occur after the introductory adjective clause.

Another issue with introductory adjective clauses occurs when the noun being modified is completely absent from the sentence:

Using the Fujita Scale, a tornado’s intensity can be rated. (Incorrect)

In this sentence, the intensity is using the Fujita Scale. This is impossible. A person must use this scale, but there are no nouns in the sentence that name people. Therefore, you would have to choose an answer choice that corrected this omission.

Given a sentence with an introductory adjective clause (which you can often identify by the presence of a comma), immediately check to make sure that the correct noun appears just after the clause.

Error Indicator: A semicolon (;)
Common Error: Incorrect use of a semicolon

A semicolon must separate two related sentences:

The birdfeeder attracts a wide variety of birds; even a painted bunting has visited on occasion. (Correct)

Notice that both sides of the semicolon contain a complete sentence:

The birdfeeder attracts a wide variety of birds. (Complete sentence)
Even a painted bunting has visited on occasion. (Complete sentence)

Errors on the GMAT occur when the semicolon is used incorrectly and one side contains a fragments:

The birdfeeder attracts a wide variety of birds; even a painted bunting. (Incorrect)

One side of the semicolon is a fragment:

The birdfeeder attracts a wide variety of birds. (Complete sentence)
Even a painted bunting. (Fragment)

If a sentence uses a semicolon, immediately check to make sure that both sides of the semicolon are complete sentences. If not, you can eliminate answer (A) and any other answer choices that do not create a complete sentence.

For more common error indicators, see Chapter 22 in the PowerScore GMAT Verbal Bible.